There are a number of circumferential characteristics or parameters of train wheels that are important for maintenance and safety purposes. These characteristics include radius and diameter of the wheel rim on which the car or locomotive rides on the track, radius and diameter of the wheel flange that extends from the rim surface, out-of-roundness of the rim and flange, eccentricity of the rim surface with respect to the flange, flat spots in the rim or flange, and spalls and tread build-up on the rim surface.
Dimensional characteristics of a train wheel rim and flange are currently measured using a device called a standard steel wheel finger gauge. This measurement technique achieves somewhat less than desired accuracy, and the time and tedium involved do not encourage measurement at the desired frequency. It has been proposed to provide an instrumented track or rail section having accelerometers for detecting flat spots in train wheels as an engine or car is driven over the track section. Although this technique has been helpful in identifying flat spots in the wheel rim, there remains a need for an automatic and non-contact method of measuring geometric characteristics such as radius, out-of-roundness and eccentricity.
It is therefore a general object of the present invention to provide a technique for measuring one or more circumferential characteristics of a test object such as a train wheel that does not require physical contact with the test object, and that may be implemented electronically for enhanced accuracy and automation. Another and more specific object of the present invention is to provide a method and apparatus for measuring one or more circumferential characteristics of train wheels, such as wheel rim and/or flange radius, that may be implemented automatically while the train wheels carry train cars over an instrumented section of track. A further object of the present invention is to provide a method and apparatus of the described character that employ microwave technology for measuring train wheel rim and/or flange radius, and other circumferential characteristics associated with rim and flange radius such as diameter, wear, flat spots and eccentricity, automatically and at high speed as the train wheels pass in succession over an instrumented section of track.